This invention generally relates to plastic containers. More specifically, this invention relates to sidewall portions of plastic containers and particularly to panels formed therein to accommodate any change in the pressure and volume inside the container during the pasteurization and after subsequent cooling of the contents of the container.
Thin-walled plastic containers with a bottle shape are popular for retaining liquid commodities, including pasteurizable liquid commodities, such as processed fruit juice. These containers are formed in a blow mold, from a material such as polyethylene terephthalate (PET), and are heat set resulting in plastic containers that have excellent mechanical strength and physical properties, and that are lightweight, inexpensive, recyclable, and manufacturable in large quantities.
Because of the numerous advantages, plastic containers for retaining pasteurizable solid commodities, such as pickles, are desirous. Unlike pasteurizable liquid commodities, pasteurizable solid commodities require a high temperature pasteurization process (hereafter just xe2x80x9chigh temperature pasteurizationxe2x80x9d), exceeding 80xc2x0 C. and often peaking above 100xc2x0 C. Because of the effects of these high temperatures on plastic containers, plastic containers used in high temperature pasteurization require different mechanical and physical properties than plastic containers used in low temperature pasteurization. Since the temperature of the commodity is raised during the pasteurization while the plastic container is sealed, high temperature pasteurization significantly increases the pressure inside the container, often more than 40 psi for a rigid (glass) container. The plastic containers of the conventional techniques in the art cannot accommodate these dramatic temperatures or the increase in pressure and these would unacceptably deform.
It is a further object of the present invention to provide a sidewall portion of a plastic container that accommodates the increase of internal pressure and volume generated by a high temperature pasteurization of a commodity in the container.
It is an additional object of the present invention to provide a sidewall portion of a plastic container that accommodates any subsequent reduction of internal pressure and volume caused by a cooling of the commodity in the plastic container.
Accordingly, this invention provides for a sidewall portion of a plastic container that overcomes the problems and disadvantages of the conventional techniques in the art. Specifically, the present invention provides for a sidewall portion of a plastic container that accommodates the increase of internal pressure and volume generated by a pasteurization of a commodity in the plastic container. The sidewall portion also accommodates any subsequent reduction of internal pressure and volume caused by a cooling of the commodity in the plastic container.
Briefly, the invention includes a sidewall portion for a plastic container used to receive a commodity and to retain the commodity during pasteurization and after cooling. The plastic container has an upper portion defining an aperture, a lower portion forming a base, and a sidewall portion unitarily connected with and extending between the upper portion and the lower portion. The sidewall portion includes a panel unitarily formed in and inwardly recessed from the sidewall, and includes a vacuum panel portion and a pressure panel, the latter being unitarily formed within the vacuum panel. The pressure panel portion is designed for movement from a first position to a second position thereby reducing the pressure generated in the container by the pasteurization of the commodity by increasing the container""s volume while avoiding any deformation of the sidewall portion beyond the panel. The vacuum panel portion is movable from a pasteurization position to a cooled position thereby realizing a reduction in pressure and volume of the container and increasing the apparent volume of the commodity in the container.
Further features and advantages of the invention will become apparent from the following discussion and accompanying drawings.